"Professor Huffmagic here with a very quick little tidbit in celebration of the new demo.So a lot of people have been asking about the hair that Dugtrio seems to have grown in his new Alolan form, and I wanted to throw a quick answer out here for you.

Anywhere that there is volcanic activity, but especially in Hawaii, there is something that occurs called Pele’s Hair.
Pele’s Hair is named after the Hawaii’n goddess of volcanoes. It is basically very thin strands of stretched basaltic glass. It is very light and often blows away and collects in large bunches.
It usually forms near large flows or fountains, and looks like lustrous golden human hair.
So as it turns out, this little dude has a totally reasonable and geologic explanation for its radical surfer doo."

Also, it's not like Dugtrio was a particularly good design to begin with.
At least this Alolan version of it is good for a laugh

Good, someone posted the reason. I know most of you are pretty dumb but do you really think they'd slap a blond wig on a pokemon without some logic behind it lol.